Inverted-F antennas are commonly used in mobile transmitter/receivers, such as cellular telephones and wireless modems for portable computers. FIG. 1 illustrates a conventional inverted-F antenna 100. As shown in FIG. 1, the inverted-F antenna 100 has a vertical ground 110 and a straight horizontal element 120. Conventional inverted-F antennas, such as the inverted-F antenna 100 of FIG. 1 can be fabricated on a printed circuit board (PCB), or using a wire or plate construction, in a well-known manner. For a detailed discussion of conventional inverted-F antennas, see, for example, Kazuhiro Hirasawa and *5 AsMisao Haneishi, "Analysis, Design, and Measurement of Small and Low-Profile Antennas," Artech House, Norwood, Mass (1992); or Kyohei Fujimoto et al., "Small Antennas," Research Studies Press, United Kingdom (1987), each incorporated by reference herein.
Inverted-F antennas are generally characterized by the distance, S, between the grounding element 110 and feeding element 130; the overall length, L, of the antenna 100; and the height, H, of the antenna 100. Impedance matching for an inverted-F antenna is obtained by adjusting the distance, S, between the grounding and feeding elements. As the size of the devices in which inverted-F antennas are utilized has decreased, the space available for such inverted-F antennas has likewise decreased. For many applications, the distance, S, between the grounding element 110 and feeding element 130 has become so small that the tuner must be extremely sensitive. In particular, the impedance matching is very difficult or too sensitive due to the small distance, S, between the grounding 110 and the feeding elements 130. In addition, the rectangular shape of conventional inverted-F antennas 100 does not provide sufficient mechanical strength for many applications.
A need therefore exists for an improved inverted-F antenna that exhibits improved impedance matching and mechanical strength. A further need exists for an improved inverted-F antenna that has a reduced overall dimension and an additional degree of freedom for tuning the impedance of the antenna.